Manufacture of particulate polyethylene

ABSTRACT

Manufacture of particulate polyethylene by polymerizing ethylene in an agitated bed of dry particulate polyethylene by means of a catalyst system comprising (1) a particulate inorganic carrier and (2) a Ziegler catalyst applied to said carrier. The catalyst system is used in the form of an intimate mixture of the catalyst system with a particulate ethylene polymer having a softening point above the polymerization temperature used, the particles in said mixture being coated with an inert organic material which is solid at 30*C but liquid at the polymerization temperature used. This process makes it possible to obtain particulate polyethylene having a desirable particle size distribution.

' Mueller-Tamm et al.

1111 3,817,969 June 18, 1974 MANUFACTURE OF PARTICULATE POLYETHYLENE Inventors: Heinz Mueller-Tamm,

Ludwigshafen; Hans Frielingsdorf, Bad Duerkheim; Johann Nick], Bad Duerkheim; Erich Kolk, Bad Duerkheim, all of Germany Badishe Anilin & Soda-Fabrik Aktiengesellschaft, Ludwigshafen/Rhein, Germany Filed: May 8, 1972 Appl. No.: 251,341

Assignee:

I U.S. Cl...'260/94.9 DA, 252/429 C, 260/949 C Int. Cl. C08f 1/56, C08f 3/06 Field of Search 260/949 C, 94.9 DA

References Cited UNITED STATES PATENTS l/l96l Daniel et al 260/949 C 7/1972 Diedrich etal...- 260/949 DA 12/1972 Kashiwa et al 260/949 DA Primary Examiner-Joseph L. Schofer l 57 ABSTRACT Manufacture of particulate polyethylene by polymerizing ethylene in an agitated bed of dry particulate polyethylene by means of a catalyst system comprising (1) a particulate inorganic carrier and (2) a Ziegler catalyst applied to said carrier. The catalyst system is used in the form of an intimate mixture of the catalyst system with a particulate ethylene polymer having a softening point above the polymerization temperature used, the particles in said mixture being coated with an inert organic material which is solid at 30C but liquid at the polymerization temperature used. This process makes it possible to obtain particulate polyethylene having a desirable particle size distribution.

7 Claims, No Drawings MANUFACTURE OF PARTICULATE POLYETHYLENE The present invention relates to a process for the manufacture of particulate polyethylene having a particle size of from 0.1 to 6.0 mm by polymerizing ethylene at temperatures of from 50 to 130C and pressures of from to 200 atmospheres in an agitated bed of dry particulate polyethylene having a particle diameter of from 0.1 to 6.0 mm by means of a catalyst system (CS) of 1. an inorganic carrier having a particle diameter of from 0.0001 to 2 mm and containing chemically combined metals and 2. a Ziegler catalyst applied to said carrier and consisting of (2.1) a catalyst component selected from the group consisting of chlorides, oxychlorides and alkoxychlorides of titanium, zirconium and vanadium and (2.2) a catalyst component selected from the group consisting of saturated metal alkyls, saturated metal alkoxyalkyls and saturated metal alkyl halides of the metals aluminum, magnesium and zinc and lithium alkyl,

provided that the ratio of the carrier (1) to catalyst component (2.1) (based on the transition metal therein) is in the range 100:0.1 to 100110, by weight, and the atomic ratio of the transition metal in catalyst component (2.1) to the metal in catalyst component (2.2) is in the range 100:1 to l00:l0,000.

Prior art processes of this type show certain advantages over other processes of comparable nature, but they suffer from the drawback that the resulting particulate polyethylene includes a relatively large fraction of particles having diameters of less than 0.5 mm. This is undesirable for two reasons, firstly, this considerably hampers agitation of the bed thus making it difficult to achieve thorough mixing of the reaction mixture, and

secondly, transportation difficulties arise when the polyethylene is worked up (unsatisfactory ingress into the machines).

It is an object of the invention to provide a process of the type defined above which shows the above drawback either not at all or to a considerably lesser extent.

We have found that this object is achieved by operating said process with a catalyst system (CS) in the form ofa mixture (M) of the catalyst system (CS) and a specific particulate ethylene polymer (EP), the particles in said mixture (M) being coated with a material selected from a specific class of materials (CM), in a specific manner.

Some further advantageous embodiments of the process have also been found, and these will be dealt with below.

Accordingly, the present inventionessentially relates to a process for the manufacture of particulate polyethylene having a particle diameter of from 0.1 to 6.0 mm by polymerizing ethylene at temperatures of from 50 to 130C and pressures of from 10 to 200 atmospheres in an agitated bed of dry particulate polyethylene having a particle diameter of from 0.1 to 6.0 mm by means of a catalyst system (CS) consisting of l. a particulate, inorganic carrier containing chemically combined metals and having a particle diameter of from 0.0001 to 2 mm and preferably from 0.0001 to 1 mm and a 2. a Ziegler catalyst applied to said carrier and consisting of (2.1) a catalyst component selected from chlorides, oxychlorides and alkoxychlorides (particularly C alkoxychlorides) of titanium, zirconium and vanadium and (2.2) a catalyst component selected from saturated metal alkyls (particularly metal C alkyls), saturated metal alkoxyalkyls (particularly metal C alkoxy C alkyls) and saturated metal alkylhalides (particularly metal C alkylchlorides) of the metals aluminum, magnesium and zinc and lithiumalkyls (particularly lithium C alkyls), provided that the ratio of carrier (1) to catalyst component (2.1), based on the transition metal therein. is in the range 10020.1 to 100:10 and preferably 10020.3 to 100:5, by weight, and the atomic ratio of the transition metal in catalyst component (2.1 to the metal in cata lyst component (2.2) is in the range 100:1 to l00:10,000, preferably 100:10 to 100:6,000. The process of the invention is characterized in that the catalyst system (CS) is used in the form of an intimate mixture (M) of the catalyst system (CS) and a particulate ethylene polymer (EP) having a particle diameter of from 0.1 to 6.0 mm and preferably from 0.1 to 1.0 mm

and having a softening point above the polymerization (CS) to (EP) 1:10 to 1:1,000 and preferably 1:25 to (CS) to (CM) 120.01 to 1:1,000 and preferably 125 to 1:10,

(EP) to (CM) 1:0.001 tolzl and preferably 1:0.1 to 110.3.

The process of the invention, apart from its special feature, may be carried out by conventional procedures and with conventional equipment, and consequently,

' detailed explanation thereof is unnecessary in this specification, although it may be mentionedthat the process is equally suitable for continuous and batchwise polymerizations.

The following remarks on the catalyst system (CS) are pertinent: (1) Suitable carriers (1) are those normally used in the art..Suitable types are described, for example, in German Printed applications Nos. 1,909,984 and 1,924,648 and the published documents of Belgian Pat. No. 705,220.

It has been found that a particularly suitable carrier is one which has been obtained by heating a material of. the following general formula for from 1 to hours and preferably from 2 to 50 hours at a temperature of from to 600C and preferably from 250 to 400C:

Me" stands for a metal or transition metal in the divalent state,

Me'" stands for a metal of transition metal in the trivalent state,

m stands for an integer of from 1 to 10 and preferably from 2 to 8 and in particular 6,

from l6 to 26 and in particular l8.

A carrier of this kind is obtained when a material of the above general formula is heated for the time stated at the temperature specified. This may be effected for example by simply heating the said material in an oven of the kind normally used for drying inorganic compounds containing water of crystallization. The desired particle size may be obtained in a simple manner, for example by milling. Metals or transition metals (Me") suitable for the present purpose and present in the divalent state are, for example, beryllium, magnesium, calcium, strontium, .barium, manganese, iron, cobalt, nickel, palladium, platinum, copper, zinc, cadmium and mercury. Of these, particularly suitable metals are magnesium, manganese, cobalt, nickel, copper, zinc and cadmium. Preferred metals of this group are magnesium, mangenese, cobalt, nickel, copper and zinc. The metals or transition metals (Me") may be present singly or as mixtures of two or more such metals. Metals or transition metals (Me') which are suitable for the present purpose and are present in the trivalent state are, for example, chromium, molybdenum, tungsten, iron, ruthenium osmium, rhenium, iridium, aluminum and gallium. Of these, particularly suitable metals are chromium, molybdenum, tungsten, iron and aluminum. Preferred metals of this group are chromium and aluminum. These metals or transition metals (Me') may be present singly or as mixtures of two or more of such metals. The materials having the said general formula are readily obtainable. A well-tried method of manufacturing such materials is for example as follows: The said metals or transition metals are used in the form of watersoluble salts, such as the chlorides, sulfates or, preferably, nitrates, and are dissolved together in water in proportions giving the desired composition of the material and obeying the stoichiometry of the general formula given above. The resulting salt solution should contain a total of about 0.5 to and preferably 1 to 4 moles of metal or transition metal ions per liter. It is heated to a temperature of from 50? to 100C and preferably from 60 to 90C and combined, over a period of from 0.5 to 120 minutes and preferably from 1 to 60 minutes, with an equivalent amount or, preferably, a slight excess ofa IM to 5M and preferably 1.5M to 4M aqueous solution of an alkali metal carbonate, in particular sodium bicarbonate, held at a temperature of from 50 to 100C and preferably from 60 to 90C. We prefer to operate using an excess of alkali metal bicarbonate equal to up to 20 percent and preferably from 0.5 to 3 percent by weight over the theoretical amount of bicarbonate. When the addition of alkali metal bicarbonate solution is complete, the mixture is stirred for from about l0 to 30 minutes and preferably from to minutes, after which the resulting precipitate is filtered off, washed with water and sucked free of excess water. In this manner, the materials of the type in question are obtained in approximately quantitative yields.

ll. The active portion of catalyst (2) and catalyst components (2.] and (2.2) may be referred to as conventional materials.

2.1. Suitable catalyst components of this kind are, for example: TiCl,, ZrCl,, VCl VOCl TiCl (OC H and TiCl (OC H Of these, particularly suitable components'are TiCl VCl, and VOCl of which TiCl, is particularly preferred. The catalyst components (2.1 may be present singly or as mixtures of two or more of such components.

2.2. Suitable catalyst components of this kind are. for example: Mg(C,H Al(C H Al(C H;) 4 9)3s a ir)a 1-. 25)=;. 2 .-,)2

Al(C H (OC H and Zn(C H Of these, particularly suitable components are Al(C ,H Al(C H 4 9)3 a i1)3 l2 25)3i 2 5)2 and Zn(C H of which the aluminum compounds are particularly preferred. The catalyst components (2.2) may be present singly or as mixtures of two or more individual components.

Application of the catalyst (2) to the carrier 1) may be carried out in conventional manner. For example, one method comprises contacting the carrier with the catalyst component (2.1) and then with the catalyst component (2.2). More specifically, this may be carried out by leaving the carrier for a number of hours in boiling catalyst component (2.1) or a boiling solution of said catalyst component, at atmospheric pressure and room temperature, and then washing it well with an inert solvent followed by drying, for example in vacuo. The resulting precatalyst may then be combined with the catalyst component (2.2) which may be in solution for example. Alternatively, the catalyst component (2.2) may be applied first to the carrier (1), followed by catalyst component (2.1 In special cases, it is even possible to apply both catalyst components,(2.l) and (2.2) to the carrier simultaneously.

The above catalyst system (CS) is used, according to the invention, in the form of a mixture (M) of the catalyst system (CS) and a specific particulate ethylene polymer (EP), the particles of the mixture (M) being coated with a material-selected from a specific class of materials (CM) in a specific manner. Suitable ethylene polymers for this purpose are conveniently, but not necessarily, of the same type as the polyethylene formed by the process. Coating materials (CM) of the desired properties are, in particular, waxy substances containing oxygen combined in ether-like and/or esterlike manner, such as polyvinyl ether waxes and ester waxes, and also silicone waxes (where there is doubtas to whether said substance is inert to the catalyst system, this may be readily ascertained by simple experiment). The said coating material (CM) may be coated onto the particles of the mixture of catalyst system and ethylene polymer in a simple manner, for example by heating the required amount of coating material (CM) in a mixer to just above its melting point, adding the mixture and stirring until the coating material (CM) has been virtually homogeneously taken up and then cooling. it is equally possible to stir a mixture of all three components and heat it to above the melting point of the coating material and then continue in the above manner.

It should be noted that usual precautions should be taken when working with catalyst components (2.1) and (2.2), catalyst (2) and the catalyst system (CS) on account of the sensitivity of these materials. That is to say, these materials should be handled with the exclusion of water (moisture) and oxygen (air).

During the development of the present invention, it was found to be desirable to use the ethylene to be polymerized in admixture with hydrogen in proportions of up to 150 parts by volume of hydrogen for every 100 parts by volume of said ethylene. This measure is conveniently employed when it is desired to obtain a polyethylene containing a minimum of particles having a diameter of more than 4 mm (tails). This effect of the hydrogen increases with its concentration and with the polymerization temperature.

EXAMPLE 1 300 g of a material having the formula:

are distributed over an area of 400 cm in a drying oven and held at a temperature of 290C for hours. This gives a carrier (1), which is milled to particles having diameters of from about 0.005 to 0.1 mm. In a conventional extractor, equipped with a flask, an extracting zone with fritted glass disk disposed above said flask, a stirrer within said extracting zone and a reflux condenser located above said extracting zone, 200 g of the carrier are charged into the zone normally used as extracting zone. 1.5 1 of TiCl are placed in the flask. The TiCl is thenbrought to the boil and kept at the boil for 7 hours. The carrier is thus in contact with TiCl vapor over this period. The TiCl -laden carrier isthen washed with n-heptane and dried at room temperature in vacuo. There is thus obtained a precatalyst in which the ratio of carrier to TiCl (based on Ti) is approximately 100:0.63, by weight. 1,080 parts by weight of this precatalyst are then homogeneously mixed with 560 parts by weight of Al(C H in a stirred vessel at room temperature. This gives the final catalyst system (CS), in which the atomic ratio of Ti to Al is approximately l00:10,000.

A heated mixer having a capacity of 8 liters is filled with 40 g of the catalyst system (CS), 850 g of a particulate polyethylene having a particle diameter offrom 0.5 to 1 mm (softening range 125 to 136C) and 100 g of pure polyvinylalkyl ether wax (melting point 50C). With constant stirring, the mixture is heated over 30 minutes to 80C and held at that temperature for 5 minutes before cooling to room temperature.

The polymerization itself is carried out continuously in a stirred reactor havinga capacity of 200 liters and containing, under steady-state conditions, a bed of 35 kg of dry particulate polyethylene having a particle diameter of from 0.1 to 6 mm. In the reactor, the ethylene pressure is kept constant at 35 atmospheres gage and the temperature is maintained at 109C. The said wax-coated mixture is fed to the reactor at a rate of 0.25 g/hr. This procedure gives 3 kg/hr ofa particulate polyethylene having a particle diameter of from 0.1 to 6 mm. The particle size distribution of the polyethylene is given in Table 1 below.

COMPARATIVE TEST Example 1 is repeated except that no polyvinylalkyl ether wax is used. The particle size distribution of the polyethylene thus obtained is also given in Table 1 below.

ent mixtures of ethylene and hydrogen are used (see Table 2 below), the total pressure being maintained at 35 atmospheres gage in each case, and that polymerization is carried out at a temper'ature of 110C and the wax-coated mixture is fed to the reactor at a rate-of 22 g/hr. The results are given in Table 2 below.

TABLE 2 Ex. Parts of H per 100 parts Sieve fractionabove 4 mm No. of ethylene by volume w/w) EXAMPLES 5 and 6 Example 1 is repeated in each case except thata mixture of ethylene and hydrogen (100:25 by volume) is used, the total pressure being maintained at 35 atmospheres gage, and that different temperatures are employed during polymerization (see Table 111 below) and the waxcoated mixture is fed to the reactor at arate of 40 g/hr. The results are given in Table 111 below.

TABLE 111 Sieve fraction above 4 mm Ex. Polymerization temperature No. (Z wlw) We claim:

l. A process for the manufacture of particulate polyethylene having a particle diameter of from 0.1 to 6.0 mm by polymerizing ethylene at temperatures of from 50 to C and pressures of from 10 to 200 atmospheres in an agitated bed of dry particulate polyethylene having a particle diameter of from 0.1 to 6.0 mm by means of a catalyst system (CS') consisting of l. a particulate, inorganic carrier containing chemically combined metals and having a particle diameter of from 0.001 to 2 mm and 2. a Ziegler catalyst applied to said carrierand consisting of 7 2.1. a catalyst component selected from chlorides, oxychlorides and alkoxychlorides of titanium, zirconium and vanadium and 2.2. a catalyst component selected from saturated metal alkyls, saturated metal all-coxyalkyls and saturated metal alkylhaides of the metals aluminum, magnesium and zinc and lithiumalk'yls provided that the ratio of carrier,( 1 to catalyst component (2.1 based on the transition metal therein, is in the range 100:0.1 to 100: 10, by weight, and the atomic ratio of the transition metal in catalyst (2.1) to the metal in catalyst component (2.2) is in the range 100:1 to 100:10,000, wherein the catalyst system (CS) is used in the form of an intimate mixture (M) of the catalyst system (CS) and a particulate ethylene polymer (EP) having a particle size of from 0.1 to 6.0 mm and having a softening point above the polymerization temperature used, the particles of said mixture (M) being coated with an organic material selected from the group consisting of a polyvinyl ether wax, an ester wax and a silicone wax (CM) which shows no ionic bonds, is inert to the catalyst system (CS) and is solid at 30C but liquidat the polymerization temperature used, the said coating being such that the following ratios by weight hold:

(C5) to (EP) 1:10 to 1:1,000

(CS) to (CM) 110.01 to 1:1,000

(EP) to (CM) 1:0.001 to 1:1.

2. A process as claimed in claim 1, wherein the catalyst system used is one in which carrier l is a material which has been obtained by heating a material of the general formula for from 1 to 100 hours at a temperature of from 150 to 600C, in which formula Me" stands for a metal or transition metal in the divalent state, Me' stands for a metal or transition metal in the trivalent state,

stands for an integer of from 1 to .10, stands for an integer of from 2 to 5,

stands for an integer of from 2 to 24,- stands for an integer of from 1 to 3, q stands for an integer of from 0 to 10, provided that 2m 3n 0 2p an integer of from 8 to 26.

3. A process as claimed in claim 2,wherein the ethylene to be polymerized is used in admixture with hydrogen so that up to 150 parts by volume of hydrogen are present for every parts by volume of said ethylene.

4. A process as claimed in claim 3 wherein said ratios by weight are:

(CS) to (EP) 1:25 to 1:50

(CS) to (CM) 1225 to 1:10

(EP) to (CM) 1:0.l-to 1:0.3.

5. A process as claimed in claim 1, wherein the-ethyl- I ene to be polymerized is used in admixture with hydrogen so that up to parts by volume of hydrogen are present for every 100 parts by volume of said ethylene.

(CS) to (EP) 1:25 to 1:50

(CS) to (CM) 1:25 to 1:10

(EP) to (CM) 120.1 .to 1:03. 

2. a Ziegler catalyst applied to said carrier and consisting of 2.1. a catalyst component selected from chlorides, oxychlorides and alkoxychlorides of titanium, zirconium and vanadium and 2.2. a catalyst component selected from saturated metal alkyls, saturated metal alkoxyalkyls and saturated metal alkylhaides of the metals aluminum, magnesium and zinc and lithiumalkyls provided that the ratio of carrier (1) to catalyst component (2.1), based on the transition metal therein, is in the range 100:0.1 to 100:10, by weight, and the atomic ratio of the transition metal in catalyst (2.1) to the metal in catalyst component (2.2) is in the range 100:1 to 100:10,000, wherein the catalyst system (CS) is used in the form of an intimate mixture (M) of the catalyst system (CS) and a particulate ethylene polymer (EP) having a particle size of from 0.1 to 6.0 mm and having a softening point above the polymerization temperature used, the particles of said mixture (M) being coated with an organic material selected from the group consisting of a polyvinyl ether wax, an ester wax and a silicone wax (CM) which shows no ionic bonds, is inert to the catalyst system (CS) and is solid at 30*C but liquid at the polymerization temperature used, the said coating being such that the following ratios by weight hold: (CS) to (EP) 1:10 to 1:1,000 (CS) to (CM) 1:0.01 to 1:1,000 (EP) to (CM) 1:0.001 to 1:1.
 2. A process as claimed in claim 1, wherein the catalyst system used is one in which carrier (1) is a material which has been obtained by heating a material of the general formula (MeII)m.(MeIII)n.(OH)o.(CO3)p.(H2O)q for from 1 to 100 hours at a temperature of from 150* to 600*C, in which formula MeII stands for a metal or transition metal in the divalent state, MeIII stands for a metal or transition metal in the trivalent state, m stands for an integer of from 1 to 10, n stands for an integer of from 2 to 5, o stands for an integer of from 2 to 24, p stands for an integer of from 1 to 3, q stands for an integer of from 0 to 10, provided that 2m + 3n o + 2p an integer of from 8 to
 26. 3. A process as claimed in claim 2, wherein the ethylene to be polymerized is used in admixture with hydrogen so that up to 150 parts by volume of hydrogen are present for every 100 parts by volume of said ethylene.
 4. A process as claimed in claim 3 wherein said ratios by weight are: (CS) to (EP) 1:25 to 1:50 (CS) to (CM) 1:2.5 to 1:10 (EP) to (CM) 1:0.1 to 1:0.3.
 5. A process as claimed in claim 1, wherein the ethylene to be polymerized is used in admixture with hydrogen so that up to 150 parts by volume of hydrogen are present for every 100 parts by volume of said ethylene.
 6. A process as claimed in claim 1 wherein said coating material (CM) is a polyvinyl alkyl ether wax.
 7. A process as claimed in claim 1 wherein said ratios by weight are: (CS) to (EP) 1:25 to 1:50 (CS) to (CM) 1:2.5 to 1:10 (EP) to (CM) 1:0.1 to 1:0.3. 